四川省夏季昼雨时空变化特征

Spatial Variation Characteristics of Annual Daytime Rainfall in Sichuan Province

摘要: 为了研究四川省昼雨夏季的区域分布特征，利用四川省126个气象站1961~2021年共61年的逐日降水观测资料，通过旋转经验正交函数分解(Rotated Empirical Orthogonal Function Decomposition，以下简称REOF分解)和集合经验模态分解(Ensemble Empirical Mode Decomposition，以下简称EEMD分解)等多种现代气候诊断统计分析方法，较为详细地分析了四川省61年来夏季昼雨的时空分布特征。研究表明：(1) 四川省夏季昼雨空间分布不均匀，昼雨空间分布均表现为东多西少、南多北少的型态，其中大值中心位于东北部，中心分别达到425 m。昼雨日数最大值分别为在川西高原南部，中心值达到60天。昼雨强度大值分布位于川东部，大致中心达到0.5 mm/h。(2) 夏季昼雨的REOF分解结果表明：分为川西南、川东北、川西北、盆地中部和川西高原5个区域。(3) 时间变化上，昼雨趋势线在20世纪90年代从低于均值变成高于均值呈上升趋势，表明昼雨线性增加；昼雨日数趋势线在20世纪90年代从高于均值变成低于均值呈下降趋势，表明降水日数线性减少；昼雨强度趋势线在20世纪90年代从低于均值变成高于均值呈上升趋势，表明降水强度线性增强。(4) EEMD分解表明夏季时：川东北部有准7年、准18年、准35年；川西北部有准5年周期变化；川西南部有准5年、准15年、准30年周期变化；川西高原有准5年、准8年周期变化；盆地中部为准6年、准30年周期变化。

Abstract: In order to study the regional distribution characteristics of daytime rainfall in Sichuan Province during summer, data from 126 meteorological stations across Sichuan Province over a period of 61 years (1961~2021) were utilized. Using modern climate diagnostic statistical analysis methods, including rotated empirical orthogonal function decomposition (REOF decomposition) and ensemble empirical mode decomposition (EEMD decomposition), a detailed analysis of the spatiotemporal distribution characteristics of summer daytime rainfall in Sichuan Province over 61 years was conducted. The research findings are as follows: (1) The spatial distribution of daytime rainfall in summer in Sichuan Province is uneven, with a pattern that shows more in the east and less in the west, and more in the south and less in the north. The maximum value centers are located in the northeast, reaching up to 425 mm. The maximum number of rainy days occurs in the southern part of the western Sichuan Plateau, with a central value of 60 days. The high intensity distribution of diurnal rainfall is found in the eastern part of Sichuan, with a roughly central value of 0.5 mm/h. (2) The REOF decomposition results of diurnal rainfall in summer indicate that it can be divided into five regions: southwestern Sichuan, northeastern Sichuan, northwestern Sichuan, central basin, and western Sichuan Plateau. (3) In terms of temporal changes, the trend line of diurnal rainfall has risen from below the mean to above the mean in the 1990s, indicating a linear increase in precipitation amount; the trend line of the number of rainy days has decreased from above the mean to below the mean in the 1990s, indicating a linear decrease in the number of rainy days; the trend line of diurnal rainfall intensity has risen from below the mean to above the mean in the 1990s, indicating a linear increase in precipitation intensity. (4) EEMD decomposition reveals that during the summer, the northeastern Sichuan region exhibits quasi-7-year, quasi-18-year, and quasi-35-year cycles; the northwestern Sichuan region shows a quasi-5-year cycle; the southwestern Sichuan region has quasi-5-year, quasi-15-year, and quasi-30-year cycles; the western Sichuan plateau features quasi-5-year and quasi-8-year cycles; and the central basin of the middle reaches has quasi-6-year and quasi-30-year cycles.